Radio receiver and method for identifying spreading codes

ABSTRACT

A grouping setting section  206  controls spreading code generation sections  207  to input a plurality of long codes into an adder  208  one by one, and thereby the plural long codes are grouped. The adder  208  adds the input plural long codes to each other at every chip in each group, and a correlation section  204  calculates a correlation value between the added long codes and a received signal. A maximum correlation value detection section  205  selects a group indicating the maximum correlation value, and the grouping setting section  206  again divides the long codes included in the selected group into a plurality of groups. By the repetition of the procedures until the long codes in a group becomes one, the long code is identified.

TECHNICAL FIELD

The present invention relates to a radio receiver and a method foridentifying spreading codes. The present invention particularly relatesto a radio receiver and a method for identifying spreading codes inmovable body radio communication employing the Code Division MultipleAccess (hereinafter referred to as “CDMA”) system.

BACKGROUND ART

Synchronous systems between base stations and asynchronous systemsbetween base stations are applicable in movable body radio communicationsystems employing the CDMA system. However, it is necessary for thesynchronous systems between base stations to use another system such asthe Global Positioning System (GPS). Consequently, the asynchronoussystems between base stations that are simpler and easier than thesynchronous systems are frequently used in the mobile radiocommunication systems.

In a conventional CDMA asynchronous cellular system between basestations, each base station holds an intrinsic long period spreadingcode (hereinafter referred to as “long code”) for identification, and amobile station identifies the long code of a cell in which the mobilestation connects a link by performing a cell search at the time of itsinitial connection and handover.

Hereinafter, FIG. 1 is referred while a conventional radio receiver andits identification method of the long code is described. FIG. 1 is ablock diagram showing the schematic configuration of the conventionalradio receiver. Incidentally, it is supposed that a radio signal isconstituted of a plurality of frames and each frame is constituted of aplurality of slots.

In FIG. 1, an antenna 1 receives radio signals, and a radio signalreception section 2 performs the reception processing of the receivedsignals. A slot/chip synchronization section 3 detects the timing whencorrelation values take the maximum value by shifting each slot of thereceived signals at every chip while multiplying each slot by a knownshort period spreading code (hereinafter referred to as “short code”)for realizing slot synchronization and chip synchronization at the sametime.

A plurality of correlation sections 4 calculate correlation values bymultiplying the received signals by spreading codes input from a switch8, which will be described later, respectively. A correlation section 5receives identified long codes from the switch 8 and performs thedespreading processing of the received signals.

A maximum correlation value detection section 6 detects the maximumcorrelation value among the plural correlation values calculated by theplural correlation sections 4. When the number of the long codes held bya spreading code generation section 7, which will be described later,namely the number of the long codes the correlation values of which withthe received signals should be calculated, is larger than the number ofthe correlation sections 4, the maximum correlation value detectionsection 6 temporarily stores the calculated correlation values anddetects the maximum correlation value after all correlation values havebeen calculated.

The spreading code generation section 7 stores a plurality of longcodes, and outputs the stored long codes to the switch 8 under thecontrol of a spreading code setting section 9, which will be describedlater. The switch 8 switches the long codes output from the spreadingcode generation section 7 to output them to any of the pluralcorrelation sections 4 or the correlation section 5 under the control ofthe spreading code setting section 9, which will be described later.

The spreading code setting section 9 controls the spreading codegeneration section 7 and the switch 8 so that the correlation values ofall of the long codes with the received signals can be calculated. Thespreading code setting section 9 identifies a long code, which is judgedby the maximum correlation value detection section 6 to be the long codegenerating the maximum correlation value, as the long code of the cellin which a link is connected, and sets the long code in the correlationsection 5. A demodulation section 10 obtains received data by performingthe RAKE combining processing of the received signals, the errorcorrection processing of them, or the like after receiving thedespreading processing by the correlation section 5.

As described above, the conventional radio receiver calculates thecorrelation values of all of the long codes with the received signals,and identifies a long code generating the maximum correlation value asthe long code of the cell in which a link is connected. The conventionalradio receiver then performs the despreading processing of the receivedsignals by the use of the identified long code to begin communication.

However, the conventional radio receiver has a problem that, because thenumber of the long codes is determined to be a fixed number inaccordance with the design of its system, if the number of thecorrelation sections is increased, the scale of the equipment becomeslarge in spite of the decrease of the time necessary for theidentification of the long codes, and if the number of the correlationsections is decreased, the time necessary for the identification of thelong codes is elongated in spite of the decrease of the scale of theequipment.

DISCLOSURE OF INVENTION

The object of the present invention is to provide a radio receiver inwhich the scale of the configuration for the calculation of thecorrelation values is suppressed to be the minimum scale, and in whichthe time necessary for the identification of its long codes isshortened.

The subject matter of the present invention is to identify a long codeby dividing a long code group including the prospective long code to beidentified into a plurality of groups, and by selecting a group havingthe maximum correlation value in the results of the addition of the longcodes in each group as the group including the long code to beidentified, and further by repeating the grouping and the narrowing downof the groups in a radio receiver.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing the schematic configuration of aconventional radio receiver;

FIG. 2A is a mimetic diagram showing an aspect of the addition of fourlong codes at every chip;

FIG. 2B is a mimetic diagram showing spectrum distributions as thecorrelation results of long codes and addition codes with receivedsignals;

FIG. 3 is a block diagram showing a schematic configuration of a radioreceiver according to the embodiment 1 of the present invention;

FIG. 4 is a block diagram showing another schematic configuration of theradio receiver of the embodiment 1 of the present invention;

FIG. 5 is a flow chart showing an operation of the identification of along code of the radio receiver according to the embodiment 1 of thepresent invention;

FIG. 6 is a block diagram showing a schematic configuration of a radioreceiver according to the embodiment 2 of the present invention;

FIG. 7 is a block diagram showing another configuration of the radioreceiver according to the embodiment 2 of the present invention;

FIG. 8 is a flow chart showing the operation of the identification of along code of the radio receiver according to the embodiment 2 of thepresent invention;

FIG. 9 is a block diagram showing a schematic configuration of a radioreceiver according to the embodiment 3 of the present invention;

FIG. 10 is a block diagram showing another schematic configuration ofthe radio receiver according to the embodiment 3 of the presentinvention;

FIG. 11 is a flow chart showing the operation of the identification of along code of the radio receiver according to the embodiment 3 of thepresent invention;

FIG. 12 is a block diagram showing a schematic configuration of a radioreceiver according to the embodiment 4 of the present invention; and

FIG. 13 is a block diagram showing another schematic configuration ofthe radio receiver according to the embodiment 4 of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

The attached drawings are referred while the embodiments of the presentinvention will be described in the following in detail.

Embodiment 1

To identify a long code is nothing but to select a long code the mutualcorrelation with received signals of which is highest and whichgenerates a peak in the correlation values when it is multiplied withthe received signals. A radio receiver generates a plurality of longcodes with its spreading code generation section for identifying thelong code.

Now, when two long codes or more are added to each other, a new longcode (hereinafter referred to as “addition code”) can be generated. FIG.2 is referred in the following while the addition of a plurality of longcodes are described. FIG. 2A is a mimetic diagram showing an aspect ofthe addition of four long codes at every chip, and FIG. 2B is a mimeticdiagram showing spectrum distributions as the correlation results oflong codes and addition codes with the received signals.

As shown in FIG. 2A, for example, in the case where four long codes A-Dare added at every chip, the long codes A-D are arranged so that theirfronts are trued up and chip data constituting the long codes are addedat every arrangement in each long code. It is supposed in the followingthat such addition is expressed as “the addition of long codes at everychip”.

It is to be noted that even if a long code having a high mutualcorrelation with a received signal is made to be an addition code bybeing added with another long code at every chip, the resulted additioncode can still have a correlation value higher than that of anadditional code generated by the mutual addition of long codes having nomutual correlation with the received signal.

That is, in FIG. 2B, the addition code generated by the addition of along code having a high mutual correlation with a received signal andanother long code does not reach the correlation result {circle around(1)} in the case where the correlation result is obtained as to a singlelong code that is to be identified and generates a peak, but theaddition code can obtain a correlation result {circle around (2)} higherthan the correlation result {circle around (3)} obtained as to a longcode having no mutual correlation whatever with the received signal.Incidentally, only the correlation result {circle around (3)} can beobtained as to the long codes having no mutual correlation whatever,however many of them are added to each other.

Consequently, it is discovered that when correlation values arecalculated about addition codes generated by grouping a plurality oflong codes and adding the grouped long codes at every chip in eachgroup, a long code to be identified is included in a group of theaddition codes exhibiting the highest correlation value.

After the group including the long code to be identified has beenselected in such a way, the similar narrowing down is performed to thelong codes included in the selected group, and then a group includingfurther less long codes is selected.

By the repetition of the narrowing down, the operations are concluded atthe time when the number of long codes included in a group becomes one.The left long code is the long code to be identified that has themaximum correlation with the received signal.

The radio receiver according to the present embodiment utilizes suchcharacteristics of the mutual correlation to identify a long code bydividing long codes into a plurality of groups, and by adding the longcodes in each group, and further by abstracting an addition code havingthe maximum correlation value from generated addition codes of eachgroup, and further by repeating the process to the abstracted group.Consequently, the number of the calculations of the correlation valueswith received signals can be decreased, and the scale of theconfiguration for the calculations of the correlation values can besuppressed to be the minimum size. In addition, the time necessary foridentifying a long code can be shortened.

FIGS. 3-5 are referred in the following while the radio receiveraccording to the present embodiment is described. FIG. 3 is a blockdiagram showing a schematic configuration of the embodiment 1 of thepresent invention, and FIG. 4 is a block diagram showing anotherschematic configuration of the embodiment 1 of the present invention.FIG. 5 is a flow chart showing the operation of the identification of along code of the radio receiver according to the embodiment 1 of thepresent invention.

Incidentally, the following two long code generation methods can beconsiderable for calculating the correlation of a plurality of longcodes with a received signal. That is, A) a method in which a pluralityof spreading code generation sections are equipped and a long codenecessary for each correlation processing is generated one by one at thetime of the correlation processing, and B) a method in which only onespreading code generation section is equipped and generated long codesare temporarily stored in a memory are considerable. FIG. 3 is referredfor the description of the former method (hereinafter referred to as“generation method A”), and FIG. 4 is referred for the description ofthe latter method (hereinafter referred to as “generation method B”).Even if either of the two generation methods is employed, there is noinfluence to the operations of the identification of a long codeaccording to the present invention.

At first, FIG. 3 is referred about the description of the case of thegeneration method A. In FIG. 3, an antenna 201 receives radio signals,and a radio signal reception section 202 performs the receptionprocessing of the received signals. A slot/chip synchronization section203 detects the timing when correlation values take the maximum value byshifting each slot of the received signals at every chip whilemultiplying each slot by the short code for realizing slotsynchronization and chip synchronization at the same time. A correlationsection 204 calculates correlation values by multiplying the receivedsignals by addition codes input from an adder 208, which will bedescribed later, or the identified long code.

A maximum correlation value detection section 205 stores the correlationvalues output from the correlation section 204 while an addition code isinput from an adder 208, which will be described later, into thecorrelation section 204, and detects the maximum correlation value.

A grouping setting section 206 controls a plurality of spreading codegeneration sections 207, which will be described later, to make eachspreading code generation section 207 generate a necessary long codeappropriately. The grouping setting section 206 then makes eachspreading code generation section 207 input the generated long code intothe adder 208, and thereby performs the grouping of the long codes.

Moreover, the grouping setting section 206 selects a group having themaximum correlation value in accordance with the results of thedetection of the maximum correlation value detection section 205. Whenonly one long code exists in the group as the result of the selection,the grouping setting section 206 identifies the long code as the longcode in the cell in which a link is to be connected, and instructs anyone of the spreading code generation sections 207 to output the longcode to the correlation section 204 through the adder 208.

The spreading code generation sections 207 store a plurality of longcodes, and outputs the stored long codes to the adder 208 under thecontrol of the grouping setting section 206. The adder 208 adds theinput plural long codes at every chip to generate an addition code, andoutputs the generated long code into the correlation section 4.

The demodulation section 209 obtains received data by performing theRAKE combining processing and the error correction processing of thereceived signals after receiving the despreading processing by means ofthe long code identified by the correlation section 204.

Next, FIG. 5 is referred while the operations of identifying a long codeof the radio receiver according to the present embodiment configuredlike shown in FIG. 3 are described.

At first, at the step (hereinafter abbreivated as “ST”) 401, a pluralityof long codes generated by the spreading code generation sections 207are output to the adder 208 one by one by means of the grouping settingsection 206, and thereby the long codes are divided into a plurality ofgroups. The grouping is determined according to the output timing ofeach spreading code generation section 207. That is, the long codes thatare added to each other by the adder 208 are grouped into the samegroup.

Next, at the ST 402, the long codes are added to each other in eachgroup by the adder 208, and addition codes of each group are generated.Next, at the ST 403, the addition codes of each group generated by theadder 208 are set in the correlation section 204 in turn. Thecorrelation section 204 then calculates the correlation values of theaddition codes with received signals.

Next, at the ST 404, the maximum correlation value detection section 205judges whether the correlation section 204 has calculated thecorrelation values of the addition codes of all of the groups with thereceived signals or not. The maximum correlation value detection section205 repeats the judgment at the ST 403 until the correlation values ofthe addition codes of all of the groups have been input into the maximumcorrelation value detection section 205.

Next, at the ST 405, the maximum correlation value detection section 205detects the maximum value among the correlation values of the additioncodes of all the groups stored in the maximum correlation valuedetection section 205 temporarily. The detection result is transmittedto the grouping setting section 206.

Next, at the ST 406, the grouping setting section 206 selects a group inwhich an addition code indicating the maximum correlation is included asthe group including the long code to be identified.

Next, at the ST 407, it is judged whether the number of the long codesincluded in the group selected at ST 406 is one or not. When the longcodes included in the selected group are two or more, the identificationoperation advances to the ST 408. When the long code is one, theidentification operation advances to ST 409.

At the ST 408, the long codes included in the group selected by thegrouping setting section 206 at the ST 406 are abstracted. And then, theidentification operation returns to the ST 401, and the grouping of thelong codes abstracted at the ST 408 is again performed. Then theoperations from the ST 401 to the ST 405 are repeated in the followingsteps until the number of the long codes selected at the ST 407 becomesone.

At the ST 409, the long code left in the group selected at the ST 406 isidentified as the long code, which generates the maximum correlationvalue with the received signal among all of the long codes, in a cell inwhich a link connection is performed. Besides the long code is set inthe correlation section 204 as the long code to be used in thedespreading processing.

Now, it is supposed, for example, that the total number of the longcodes is 512 and the number of the spreading code generation sections207 is 64. Then, one group is constituted by 64 long codes and all ofthe long codes are divided into the eight groups, group 1 to group 8, atthe ST 401.

Next, the long codes grouped into each group of the groups 1-8 are addedin respective groups, and addition codes of respective groups 1-8 aregenerated at the ST 402.

Then, at the ST 403, the correlation value with a received signal iscalculated as to each addition code, and at the ST 405, it is judgedwhich correlation value is the largest among the correlation values ofthe groups 1-8. And then, at the ST 406, a group the correlation valueof which is the largest is selected.

Because there are 64 long codes in the selected group, theidentification operation advances to the ST 408 from the ST 407. At theST 408, the 64 long codes included in the selected group are abstracted,and then at the ST 401, the division of the long codes into groups eachof which include eight long codes is performed. And then, the additionof the long codes at every group, the calculation of the correlationvalues with the received signal, and the selection of one group areperformed.

The eight long codes included in the selected group are again dividedinto eight groups. This time, one long code is included in each group.

In this case, the calculations of correlation values with the receivedsignal are performed 24 times until the long code has been identified.The processes of the calculations of the correlation values decrease incomparison with the conventional case where the correlation values witha received signal are calculated one by one for all of the 512 longcodes.

Next, FIG. 4 is referred while the case in which the aforesaidgeneration method B is used for the generation of long codes isdescribed. Incidentally, the configurations similar to those shown inFIG. 3 are designated by the same reference numerals as those in FIG. 3,and the detailed descriptions to them are omitted.

In FIG. 4, the maximum correlation value detection section 205 storescorrelation values output from the correlation section 204 while longcodes are input into the correlation section 204 from a switch 304,which will be described later, and detects the maximum correlationvalue.

A spreading code generation section 301 stores a plurality of longcodes, and outputs the stored long codes to a switch 302, which will bedescribed later, under the control of the grouping setting section 206.The switch 302 outputs the long codes output from the spreading codegeneration section 301 to any of a plurality of adders 303 or thecorrelation section 204 under the control of the grouping settingsection 206, which will be described later.

The grouping setting section 206 groups long codes by controlling thespreading code generation section 301 and the switch 302 to make thelong codes output from the spreading code generation section 301 beinput into any of the plural adders 303.

Besides, the grouping setting section 206 selects a group having themaximum correlation value in accordance with the results of thedetection of the maximum correlation value detection section 205. Whenonly one long code exists in the group as the result of the selection,the grouping setting section 206 identifies the long code as the longcode in the cell in which a link is to be connected, and instructs theswitch 302 to output the identified long code to the correlation section204.

The adders 303 add the input plural long codes at every chip, andgenerate new codes to output the generated codes into the switch 304.Incidentally, the number of the adders 303 is arbitrary.

The switching of the switch 304 is controlled by the slot/chipsynchronization section 203 to output the addition codes of each group,which are outputs of the plural adders 303, to the correlation section204.

The demodulation section 209 obtains received data by performing theRAKE combining processing and the error correction processing of thereceived signals after receiving the despreading processing with thelong code identified by the correlation section 204.

Next, FIG. 5 is referred while the operations of the identification of along code of the radio receiver according to the present embodimentconfigured like shown in FIG. 4 are described.

At first, at the ST 401, all of the long codes held by the spreadingcode generation section 301 are divided into a plurality of groups bythe grouping setting section 206. The switch 302 performs the groupingby outputting the long codes to different adders 303.

Next, at the ST 402, each adder 303 adds the long codes input intodifferent adders 303 at every group to each other, and generatesaddition codes of each group.

Next, at the ST 403, the addition code of each group generated by eachadder 303 is set in the correlation section 204 in turn by the switch304, the switching of which is controlled by the slot/chipsynchronization section 203. The correlation section 204 then calculatesthe correlation values of the addition codes with received signals.

Next, at the ST 404, the maximum correlation value detection section 205judges whether the correlation section 204 has calculated thecorrelation values of the addition codes of all of the groups with thereceived signals or not. The maximum correlation value detection section205 repeats the judgment at the ST 403 until the correlation values ofthe addition codes of all of the groups have been input into the maximumcorrelation value detection section 205.

Incidentally, if the number of the groups divided by the groupingsetting section 206 is larger than the number of the adders 303, theadders 303 are used in conformity with the time sharing control methodand the calculations of the correlation values are divided into severaltimes of operations.

Next, at the ST 405, the maximum correlation value detection section 205detects the maximum value among the correlation values of the additioncodes of all the groups stored in the maximum correlation valuedetection section 205 temporarily. The detection results are transmittedto the grouping setting section 206.

Next, at the ST 406, the grouping setting section 206 selects a group inwhich an addition code indicating the maximum correlation is included asthe group including the long code to be identified.

Next, at the ST 407, it is judged whether the number of the long codesincluded in the group selected at ST 406 is one or not. When the longcodes included in the selected group are two or more, the identificationoperation advances to the ST 408. When the long code is one, theidentification operation advances to ST 409.

At the ST 408, the long codes included in the group selected by thegrouping setting section 206 at the ST 406 are abstracted. And then, theidentification operation returns to the ST 401, and the grouping of thelong codes abstracted at the ST 408 is again performed. Then theoperations from the ST 401 to the ST 405 are repeated in the followingsteps until the number of the long codes selected at the ST 407 becomesone.

At the ST 409, the long code left in the group selected at the ST 406 isidentified as the long code, which generates the maximum correlationvalue with the received signal among all of the long codes, in a cell inwhich a link connection is performed. Besides the long code is set inthe correlation section 204 as the long code to be used in thedespreading processing.

Now, it is supposed, for example, that the total number of the longcodes is 512 and the number of the adders 303 is 16 and further thegrouping of the long codes is performed into eight groups at every time.Then, at the ST 401, eight adders are used for the grouping of the longcodes into eight groups, group 1-8, each of which includes 64 longcodes.

Next, the long codes grouped into the groups 1-8 are added in eachgroup, and addition codes of respective groups 1-8 are generated at theST 402.

Then, at the ST 403, the correlation value with a received signal iscalculated regarding each addition code, and at the ST 405, it is judgedwhich correlation value is the largest among the correlation values ofthe groups 1-8. And then, at the ST 406, a group the correlation valueof which is the largest is selected.

Because there are 64 long codes in the selected group, theidentification operation advances to the ST 408 from the ST 407. At theST 408, the 64 long codes included in the selected group are abstracted,and then at the ST 401, the division of the long codes into eight groupsis again performed. And then, the addition of the long codes at everygroup, the calculation of the correlation values with the receivedsignal, and the selection of one group are performed.

The eight long codes included in the selected group are again dividedinto eight groups. This time, one long code is included in each group.

In this case, the calculations of correlation values with the receivedsignal are performed 24 times until the long code has been identified.The processes of the calculations of the correlation values are lessthan that of the conventional case where the correlation values with areceived signal are calculated one by one for all of the 512 long codes.

As described above, according to the present embodiment, because longcodes are identified by repeating the operations of dividing the longcodes into a plurality of groups and adding the divided long codes toeach other and further selecting a group having the maximum additioncode among the addition code of every group, the number of thecalculations of the correlation values with received signals can bedecreased, and the scale of the configuration for the calculations ofthe correlation values can be suppressed to be the minimum size. Inaddition, the time necessary for identifying a long code can beshortened.

Embodiment 2

A radio receiver according to the present embodiment has a configurationsimilar to that of the embodiment 1. In addition, when the differencebetween the maximum value and the next maximum value of the correlationvalues of the addition codes in each group is smaller than an arbitrarythreshold value, the radio receiver divides each group to increase thenumber of the groups, and again detects the maximum value.

Even if a long code having a high mutual correlation with a receivedsignal is added with other long codes in a chip, the added long code canhave a correlation value higher than that of a code generated by theaddition of long codes having no mutual correlation with the receivedsignal to each other. However, the peak value of the correlation valuesof the added long codes becomes lower than that of a single long code tobe identified.

Moreover, there is a case where the long code to be identified isinfluenced by other long codes to weaken its correlation value.Consequently, there occurs a case where it is impossible to judge whichgroup the long code to be identified is included to because any of thecorrelation values of the addition codes of every group is low in somegrouping methods of the long codes, or a case where the correlationvalue of the addition code of a group not including the long code to beidentified is the maximum correlation value in some grouping methods ofthe long codes.

Accordingly, the radio receiver according to the present embodimentdetects the maximum correlation value again after increasing the numberof groups by dividing every group when the difference between themaximum value and the next maximum value of the correlation value of theaddition code of each group is equal to or less than an arbitrarythreshold value.

In the following, FIGS. 6-8 are referred while the radio receiveraccording to the present embodiment is described. FIG. 6 is a blockdiagram showing a schematic configuration of the embodiment 2 of thepresent invention, and FIG. 7 is a block diagram showing anotherschematic configuration of the embodiment 2 of the present invention.FIG. 8 is a flow chart showing the operations of the identification of along code of the radio receiver according to the embodiment 2 of thepresent invention. Incidentally, the configurations similar to those ofthe embodiment 1 are designated by the same reference marks as those inthe embodiment 1, and their detailed descriptions are omitted.

At first, FIG. 6 is referred about the description in the case where thegeneration of long codes is performed in conformity with the aforesaidgeneration method A. In FIG. 6, a next maximum correlation valuedetection section 501 operates in parallel with the maximum correlationvalue detection section 205 when the maximum correlation value detectionsection 205 is operating. The next maximum correlation value detectionsection 501 temporarily stores correlation values of additional codes ofthe whole group output from the correlation section 204, and detects thesecond largest value among the stored correlation values.

A subtracter 502 performs the subtraction processing between the maximumvalue among the correlation values of the addition codes of the wholegroup output from the maximum correlation value detection section 205and the next maximum value among the correlation values of the additioncodes of the whole group output from the next maximum correlation valuedetection section 501. The subtracter 503 performs the subtractionprocessing between the differences between the maximum correlationvalues and the next maximum correlation values output from thesubtracter 502 and an arbitrary threshold value.

A group number setting section 504 judges the subtraction results of thesubtracter 503, and instructs the grouping setting section 206 toincrease the number of groups by dividing each group when the differenceis smaller than the threshold value, and instructs nothing to thegrouping setting section 206 when the difference is larger than thethreshold value.

It is possible to increase the number of the groups by decreasing thenumber of the spreading code generation sections 207 that is operated todecrease the number of the long codes to be added at the same time inthe adder 208, and by increasing the number of times of the additionprocessing.

Next, FIG. 8 is referred while the operation of identifying a long codeof the radio receiver according to the present embodiment is described.In FIG. 8, the ST 701 to ST 704 are the same as the corresponding stepsin FIG. 4 concerning the embodiment 1, consequently the descriptionsabout them are omitted.

At the ST 705, the maximum correlation value detection section 205 andthe next maximum correlation value detection section 501 detect themaximum correlation value and the next maximum correlation value amongthe correlation values of the addition codes at every group calculatedby the correlation section 204.

Next, at the ST 706, the subtracter 502 and the subtracter 503 judgeswhich is larger of the difference between the maximum value and the nextmaximum value in the correlation values of the addition codes at everydetected group and an arbitrary threshold value.

When it is judged that the difference between the maximum value and thenext maximum value is smaller than the threshold value in the judgmentat the ST 706, the detection of a peak is judged to be impossible, andthe identification operation advances to the ST 707. At the ST 707, thegroup number setting section 504 instructs the grouping setting section206 to divide each group to increase the number of the groups and tobegin the detection of the maximum value again.

For example, if eight groups at that time are divided into sixteengroups, the number of the long codes included in each group decreases toa half of the original number, and the influence of other long codes byaddition to the long code to be identified decreases. Consequently, thepeak becomes easy to detect.

When the difference between the maximum value and the next maximum valueis larger than the threshold value at the judgment at the ST 706, it isjudged that a peak has been detected, and the identification operationadvances to the ST 708. At the ST 708, a group the addition code ofwhich takes the maximum value is selected as the group including thelong code to be identified. The following processes from the ST 709 tothe ST 711 are the same as those of the ST 407 to the ST 409 in FIG. 4concerning the embodiment 1, consequently, their descriptions areomitted. Incidentally, the increasing procedures of the number of groupsby the division of each group are repeated until the difference betweenthe maximum value and the next maximum value becomes smaller than thethreshold value.

Furthermore, FIG. 6 shows a configuration in which the aforesaidgeneration method B is used for the generation of long codes. Becauseeach configuration and each operation are the same as those of theaforesaid configuration, the detailed description thereof is omitted.

As described above, the present embodiment judges that a peak is notdetected when the difference between the maximum value and the nextmaximum value of the correlation values of the addition codes at everygroup is smaller than an arbitrary threshold value, and divides eachgroup to increase the number of groups and to decrease the number of thelong codes included in each group, and then detects the maximumcorrelation value again. Consequently, the embodiment can preciselydetect a peak, and then can precisely detect a long code to beidentified.

Incidentally, in the description of the radio receiver according to thepresent embodiment, the description has been given to a case where themaximum correlation value detection section 205 and the next maximumcorrelation value detection section 501 are provided separately, butthey may be realized as the same component as long as the maximum valueand the next maximum value can be detected.

Embodiment 3

The radio receiver according to the present embodiment has aconfiguration similar to that of the embodiment 2. But, the embodimentchanges the combination of the long codes included in each group anddetects the maximum value again when the difference between the maximumvalue and the next maximum value of the correlation value of theaddition code of each group is smaller than an arbitrary thresholdvalue.

Even if a long code having a high mutual correlation with a receivedsignal is added with other long codes at every chip, the added long codecan have a correlation value higher than that of a code generated by theaddition of long codes having no mutual correlation with the receivedsignal to each other. However, the peak value of the correlation valuesof the added long codes becomes lower than that of a single long code tobe identified.

Moreover, there is a case where the long code to be identified isinfluenced by other long codes to weaken its correlation value.Consequently, there occurs a case where it is impossible to judge whichgroup the long code to be identified is included to because any of thecorrelation values of the addition codes of every group is low in somegrouping methods of the long codes, or a case where the correlationvalue of the addition code of a group not including the long code to beidentified is the maximum correlation value in some grouping methods ofthe long codes.

Accordingly, the radio receiver according to the present embodimentdetects the maximum correlation value again after grouping the longcodes again when the difference between the maximum value and the nextmaximum value of the correlation value of the addition code of eachgroup is equal to or less than an arbitrary threshold value.

FIGS. 9-11 are referred in the following while the radio receiveraccording to the present embodiment is described. FIG. 9 is a blockdiagram showing a schematic configuration of a radio receiver accordingto the embodiment 3 of the present invention, and FIG. 10 is a blockdiagram showing another schematic configuration of the radio receiveraccording to the embodiment 3 of the present invention. FIG. 11 is aflow chart showing the operation of the identification of a long code ofthe radio receiver according to the embodiment 3 of the presentinvention. Incidentally, the configurations similar to those of theembodiment 2 are designated by the same reference marks, and theirdetailed descriptions are omitted.

At first, FIG. 9 is referred about the description of a case where longcodes are generated in conformity with the aforementioned generationmethod A. In FIG. 9, a grouping setting section 801 changes thecombination of long codes so that the long codes included in each groupare changed while not changing the number of groups when the differencebetween the maximum value and the next maximum value of the correlationvalue of the addition code of each group is smaller than a thresholdvalue, and the grouping setting section 801 selects a group to which along code to be identified belongs when the difference between themaximum value and the next maximum value is larger than the thresholdvalue.

The changes of the combinations of long codes are performed inconformity with the instructions and the control of the grouping settingsection 801 to the spreading code generation sections 207 to change thegeneration order of spread codes.

Next, FIG. 11 is referred while the operation of the identification oflong codes of the radio receiver according to the present embodiment isdescribed. In FIG. 11, because the operations from the ST 1001 to the ST1005 are the same as those at the ST 701 to ST 705 in FIG. 8 concerningthe embodiment 2, the descriptions of the operations from the ST 1001 tothe ST 1005 are omitted.

At the ST 1006, the subtracter 503 judges which is larger of thedifference between the maximum correlation value and the next maximumcorrelation value, the difference being output from the subtracter 502,and an arbitrary threshold value.

When the difference is smaller than the threshold value at the ST 1006,it is judged that the detection of a peak is impossible, and theidentification operation returns to the ST 1001. In this case, no groupis selected, namely the number of the groups is not changed, and thenthe grouping is again started by the grouping setting section 801, andconsequently the combinations of long codes included in each group arechanged.

Because long codes to be added to a long code to be identified arechanged when the combinations of the long codes included in each groupare changed, if a long code that has weakened the mutual correlation ofthe long code to be identified moves to a group different from the groupto which the long code to be identified belongs, the mutual correlationof the long code to be identified emerges in the correlation value ofthe addition code, and thereby a peak becomes possible to be detected.

When the maximum value is larger than the threshold value at the ST1006, it is judged that a peak has been detected. Then, theidentification operation advances to the ST 1007, and a group theaddition code of which exhibits the maximum value is selected as thegroup including the long code to be identified. Because the processingfrom the ST 1008 to the ST 1010 is the same as that of the ST 709 to ST711 in FIG. 8 concerning the embodiment 2, the description of theprocessing is omitted. Incidentally, the re-grouping is repeated untilthe maximum value becomes larger than the threshold value.

Furthermore, a configuration in the case where the aforesaid generationmethod is used for the generation of the long codes is shown in FIG. 10.Each configuration and its operation are the same as the alreadydescribed configuration, and consequently the detailed description ofthe configuration is omitted.

As described above, according to the present embodiment, it is judgedthat no peak is detected when the difference between the maximum valueand the next maximum value of the correlation value of the addition codeat every group is smaller than an arbitrary threshold value, and thegrouping of long codes is again started for the detection of the maximumcorrelation value after the combinations of the long codes included ineach group has been changed, and consequently a peak can precisely bedetected, and thereby the long code to be identified can precisely bedetected.

Incidentally, the number of the long codes to be replaced and the methodof the replacement at the time of the replacement of the long codesincluded in each group are quite arbitrary.

Embodiment 4

A radio receiver according to the present embodiment has a configurationsimilar to that of the embodiment 1. In addition, when the differencebetween the maximum value and the next maximum value of the correlationvalue of the addition code in each group is smaller than an arbitrarythreshold value, the radio receiver divides each group to increase thenumber of the groups. Or, when the difference between the maximum valueand the next maximum value of the correlation value of the addition codein each group is smaller than an arbitrary threshold value, the radioreceiver changes the combinations of long codes included in each group,and again detects the maximum value.

Hereinafter, FIG. 12 and FIG. 13 are referred while the radio receiveraccording to the present invention is described. FIG. 12 is a blockdiagram showing a schematic configuration of the receiver according tothe embodiment 4 of the present invention, and FIG. 13 is a blockdiagram showing another schematic configuration of the receiveraccording to the embodiment 4 of the present invention. Incidentally,the configurations similar to those of the embodiment 2 and theembodiment 3 are designated by the same reference marks as those in theembodiments 2 and 3, and the detailed descriptions of the configurationsare omitted.

At first, FIG. 12 is referred about the description in the case wherethe generation of long codes is performed in conformity with theaforesaid generation method A. In the radio receiver according to thepresent embodiment, likewise the embodiment 2, the subtracter 502performs the subtraction processing of the maximum value of thecorrelation value of the addition code in each group output from themaximum correlation value detection section 205 and the next maximumvalue output from the next maximum correlation value detection section501, and the subtracter 503 performs the subtraction processing ofoutputs from the subtracter 502 and an arbitrary threshold value. Whenthe difference between the maximum value and the next maximum value isequal to the threshold value or less, the group number setting section504 instructs a grouping setting section 1101 to divide each group toincrease the number of groups and to perform the detection of themaximum correlation value again.

Or, in the radio receiver according to the present embodiment, likewisein the embodiment 3, the subtracter 502 performs the subtractionprocessing of the maximum value of the correlation value of the additioncode in each group output from the maximum correlation value detectionsection 205 and the next maximum value output from the next maximumcorrelation value detection section 501, and the subtracter 503 performsthe subtraction processing of outputs from the subtracter 502 and anarbitrary threshold value. When the difference between the maximum valueand the next maximum value is equal to the threshold value or less, agrouping setting section 1101 changes the combinations of long codes byreplacing the long codes included in each group, and the maximumcorrelation value is again detected.

Moreover, a configuration in a case where the aforesaid generationmethod B is used for the generation of long codes is shown in FIG. 13.Each configuration and operation are similar to the already describedeach configuration, their detailed descriptions are omitted.

As described above, the radio receiver according to the presentembodiment performs both of or either of the division of each group andthe replacement of long codes included in each group when no peak valueis detected from the correlative value of the addition code of eachgroup, and consequently, the selection of a group including a long codeto be identified can be performed more efficiently, and thereby the timenecessary for the identification of the long code can be shortened.

Incidentally, in the aforementioned embodiments 1-4, the number of thelong codes is set to be the n-th power of 2 because in almost all thecase the number of the long codes is the n-th power of 2. However, thepresent invention is not limited to the application of the condition,but the present invention can be applied to such a case where the totalnumber of the long codes is odd, and the number of the long codesincluded in each group is consequently not uniform. Moreover, it issimilarly not necessary that the number of the groups is an even number.

Furthermore, in the aforesaid embodiments 1-4, the descriptions aregiven to a case where all groups are divided into just half of them todouble their numbers when they are grouped. However, the application ofthe present invention is not restricted to the aforesaid condition, butit is not necessary to divide all of the groups. Moreover, it is alsonot necessary to divide them evenly. However, it is preferable that allof the groups are divided evenly.

Furthermore, in the aforesaid embodiments 1-4, the descriptions aregiven to a case where only one correlation section is equipped, but twoor more correlation sections may be equipped for the sake of theshortening of the time necessary for identifying long codes. However,because it can considerable that the time can be shortened enough by themethod for the identification of long codes according to the presentinvention, it is more preferable to minimize the scale of its hardwareby suppressing the configuration for calculating correlation values tobe minimum.

Furthermore, in the aforesaid embodiments 1-4, the descriptions aregiven to a case where two kinds of spreading codes, long codes and shortcodes, are used, but the application of the present invention is notlimited to the case. That is, the present invention can always beapplied to the cases where a base station intrinsic spreading code to beconnected with a link is identified among a plurality of spreadingcodes.

Furthermore, in the aforesaid embodiments 3 and 4, the descriptions aregiven to the cases where the replacement is performed when thedifference between the maximum correlation value and the next maximumcorrelation value is smaller than an arbitrary threshold value. However,it is also possible to perform the replacement when the maximumcorrelation value is smaller than the arbitrary threshold value.

Furthermore, it is also possible that the radio receiver of the presentinvention is applied to a communication system such as M-array spectrumspreading communication in which transmission data and reception dataare modulated and demodulated on the basis of the distinction of thekinds of spreading codes.

A radio receiver of the present invention comprising: an additionspreading code generation section for dividing an input spreading codegroup into at least two groups and adding spreading codes included ineach group to each other at every chip to generate new spreading codes;a group selection section for calculating correlation values betweeneach of the spreading codes generated by the addition spreading codegeneration section and a received signal and selecting a group having amaximum correlation value among the calculated correlation values, and acontrol section for judging whether a number of spreading codes includedin the group selected by the group selection section is one or not, andinputting all of the spreading codes included in the selected group intothe spreading code generation section when the number of the spreadingcodes is two or more, and further setting the spreading codes includedin the selected group to be used at despreading processing to thereceived signal when the number of the spreading codes is one.

According to the configuration, a long code is identified by repeatingthe division of the long codes into a plurality of groups, the additionof the divided long codes to each other, and the selection of a groupindicating the maximum correlation value among the addition code of eachgroup. Consequently, the number of times of the calculations of thecorrelation values with a received signal can be decrease. Thereby, theconfiguration for calculating the correlation values can be suppressedto the minimum scale, and moreover the time necessary for theidentification of a long code can be shortened.

The radio receiver of the present invention employs a configuration inthe aforesaid configuration, wherein the addition spreading codegeneration section includes a division section for dividing at least onegroup among each of the groups after being grouped at every arbitrarynumber of the spreading codes to increase a number of groups, and thegroup selection section includes a subtraction processing section forcalculating a next maximum correlation value being largest next to themaximum correlation value and a difference between the next maximumcorrelation value and the maximum correlation value, and a divisioninstruction section for instructing the division section to performdivision when the difference is smaller than an arbitrary thresholdvalue.

According to the configuration, a peak is judged not to be detected whenthe difference between the maximum value and the next maximum value ofthe correlation value of the addition code in each group is smaller thanan arbitrary threshold value, and each group is divided so that thenumber of groups is increased and the number of long codes included ineach group is decreased. And then, the maximum correlation value isagain detected. Consequently, the peak can accurately be detected, andthe long code to be identified can correctly be detected.

The radio receiver according to the present invention employs aconfiguration in the aforesaid configuration, wherein the additionspreading code generation section includes a spreading code replacementsection for changing a combination of the spreading codes included ineach of the groups after being grouped, the group selection sectionincludes a subtraction processing section for calculating a next maximumcorrelation value being a correlation value largest next to the maximumcorrelation value and a difference between the next maximum correlationvalue and the maximum correlation value, and a replacement instructionsection for instructing the spreading code replacement section toperform the replacement when the difference is smaller than an arbitrarythreshold value.

According to the configuration, a peak is judged not to be detected whenthe difference between the maximum value and the next maximum value ofthe correlation value of the addition code in each group is smaller thanan arbitrary threshold value, and the combination of the long codesincluded in each group is changed, and grouping is again started of thedetection of the maximum correlation value again. Consequently, the peakcan accurately be detected, and the long code to be identified cancorrectly be detected.

The radio receiver according to the present invention employs aconfiguration in the aforesaid configuration, wherein the additionspreading code generation section includes a division section fordividing at least one group among each of the groups after being groupedat every arbitrary number of the spreading codes to increase a number ofthe groups and a spreading code replacement section for changingcombinations of the spreading codes included in each of the groups afterbeing grouped or being divided, and the group selection section includesa subtraction processing section for calculating a next maximumcorrelation value being a correlation value largest next to the maximumcorrelation value and calculating a difference between the next maximumcorrelation value and the maximum correlation value, a divisioninstruction section for instructing the division section to perform thedivision when the difference is smaller than an arbitrary thresholdvalue, and a replacement instruction section for instructing thespreading code replacement section to perform the replacement when adifference between the next maximum correlation value and the maximumcorrelation value is smaller than an arbitrary threshold value.

According to the configuration, when a peak is not detected in thecorrelation value of the addition code of each group, at least either ofthe division of each group and the replacement of the long codesincluded in each group for increasing the number of groups is performed.Consequently, the selection of a group including a long code to beidentified can be performed more efficiently, and then the timenecessary for the identification of the long code can be shortened.

A method for identifying a spreading code according to the presentinvention comprising: an addition spreading code generation step fordividing a spreading code group into at least two groups and addingspreading codes included in each group to each other at every chip togenerate new spreading codes; a group selection step for calculatingcorrelation values between each of the spreading codes generated by theaddition spreading code generation means and a received signal andselecting a group having a maximum correlation value among thecalculated correlation values, and a control step for judging whether anumber of spreading codes included in the group selected at the groupselection step is one or not, and returning all of the spreading codesincluded in the selected group into the addition spreading codegeneration step when the number of the spreading codes is two or more,and further setting the spreading codes included in the selected groupto be used at despreading processing to the received signal when thenumber of the spreading code is one.

According to the method, because the long codes are divided into aplurality of groups to be added to each other, and a group indicatingthe maximum correlation value among addition code of each group isselected, and further these procedures are repeated to identify the longcode, the number of times of the calculation of correlation values witha received signal can be decreased, and thereby the configuration forcalculating the correlation values can be suppressed to be the minimumscale and the time necessary for the identification of the long code canbe shortened.

The method for identifying a spreading code according to the presentinvention in the aforesaid method, wherein in the group selection step,a next maximum correlation value being a correlation value largest nextto the maximum correlation value is calculated, and a difference betweenthe next maximum correlation value and the maximum correlation value iscalculated, and further the addition spreading code generation step iscontrolled so that at least one group of each of the groups after beinggrouped is divided at every arbitrary number of the spreading codes toincrease a number of the groups when the difference is smaller than anarbitrary threshold value.

According to the method, when the difference between the maximum valueand the next maximum value of the correlation value of the addition codein each group is smaller than an arbitrary threshold value, a peak isjudged not to be detected, and each group is divided. Thereby the numberof the groups increases, and the number of the long codes included ineach group decreases. After that, the maximum correlation value is againdetected. Consequently, the detection of the peak can precisely beperformed, and the long code to be identified can correctly be detected.

The method for identifying a spreading code according to the presentinvention in the aforesaid method, wherein in the group selection step,the addition spreading code generation step is controlled so thatcombinations of the spreading codes included in each of the groups afterbeing grouped are changed when the difference between the next maximumcorrelation value and the maximum correlation value is smaller than anarbitrary threshold value.

According to the method, when the difference between the maximum valueand the next maximum value of the correlation value of the addition codein each group is smaller than an arbitrary threshold value, a peak isjudged not to be detected, and the combination of long codes included ineach group is changed for the re-grouping of the long codes. And thenthe maximum correlation value is again detected. Consequently, thedetection of the peak can precisely be performed, and the long code tobe identified can correctly be detected.

The method for identifying a spreading code according to the presentinvention in the aforesaid method, wherein in the group selection step,a next maximum correlation value being a correlation value largest nextto the maximum correlation value is calculated, and a difference betweenthe next maximum correlation value and the maximum correlation value iscalculated, and increase of a number of the groups by dividing at leastone group of each of the groups after being grouped at every arbitrarynumber of the spreading codes is instructed when the difference issmaller than an arbitrary threshold value, and/or change of combinationsof the spreading codes included in each of the groups after beinggrouped or after being divided is instructed when the difference betweenthe next maximum correlation value and the maximum correlation value issmaller than the arbitrary threshold value.

According to the method, when a peak is not detected in the correlationvalue of the addition code of each group, at least one of the proceduresof the division of each group for the increase of the number of groupsand the replacement of the long codes included in each group isperformed. Consequently, the selection of a group including a long codeto be identified can be performed more efficiently, and the timenecessary for the identification of the long code can be shortened.

As described above, according to the present invention, because a longcode is identified by repeating the grouping and the narrowing down of along code group being the prospective long code to be identified, theconfiguration for calculating correlation values can be suppressed to bethe minimum scale, and the time necessary for identifying a long codecan be shortened.

This application is based on the Japanese Patent Application No. HEI11-169698 filed on Jun. 16, 1999, entire content of which is expresslyincorporated by reference herein.

Industrial Applicability

The present invention can be applied to a communication terminal or abase station apparatus in a digital radio communication system.According to these configurations, in an opponent station ofcommunication, a long code is identified by repeating the grouping andthe narrowing down of a long code group being a prospective long code tobe identified. Consequently, the configuration for calculatingcorrelation values can be suppressed to be the minimum scale, and thetime necessary for identifying the long code can be shortened.

What is claimed is:
 1. A radio receiver comprising: addition spreadingcode generation means for dividing an input spreading code group into atleast two groups and adding spreading codes included in each group toeach other at every chip to generate new spreading codes; groupselection means for calculating correlation values between each of thespreading codes generated by said addition spreading code generationmeans and a received signal and selecting a group having a maximumcorrelation value among the calculated correlation values, and controlmeans for judging whether a number of spreading codes included in thegroup selected by said group selection means is one or not, andinputting all of the spreading codes included in the selected group intosaid addition spreading code generation means when the number of thespreading codes is two or more, and further setting the spreading codesincluded in the selected group to be used at despreading processing tothe received signal when the number of the spreading code is one.
 2. Theradio receiver according to claim 1, wherein said addition spreadingcode generation means includes a division section for dividing at leastone group among each of the groups after being grouped at everyarbitrary number of the spreading codes to increase a number of groups,and said group selection means includes a subtraction processing sectionfor calculating a next maximum correlation value being largest next tothe maximum correlation value and a difference between the next maximumcorrelation value and the maximum correlation value, and a divisioninstruction section for instructing the division section to performdivision when the difference is smaller than an arbitrary thresholdvalue.
 3. The radio receiver according to claim 1, wherein said additionspreading code generation means includes a spreading code replacementsection for changing a combination of the spreading codes included ineach of the groups after being grouped, said group selection meansincludes subtraction processing section for calculating a next maximumcorrelation value being a correlation value largest next to the maximumcorrelation value and a difference between the next maximum correlationvalue and the maximum correlation value, and a replacement instructionsection for instructing the spreading code replacement section toperform the replacement when the difference is smaller than an arbitrarythreshold value.
 4. The radio receiver according to claim 1, whereinsaid addition spreading code generation means include a division sectionfor dividing at least one group among each of the groups after beinggrouped at every arbitrary number of the spreading codes to increase anumber of the groups, and a spreading code replacement section forchanging combinations of the spreading codes included in each of thegroups after being grouped or being divided, and said group selectionmeans include a subtraction processing section for calculating a nextmaximum correlation value being a correlation value largest next to themaximum correlation value and calculating a difference between the nextmaximum correlation value and the maximum correlation value, a divisioninstruction section for instructing the division section to perform thedivision when the difference is smaller than an arbitrary thresholdvalue, and a replacement instruction section for instructing thespreading code replacement section to perform the replacement when adifference between the next maximum correlation value and the maximumcorrelation value is smaller than an arbitrary threshold value.
 5. Acommunication terminal equipped with a radio receiver, said radioreceiver comprising: addition spreading code generation means fordividing an input spreading code group into at least two groups andadding spreading codes included in each group to each other at everychip to generate new spreading codes; group selection means forcalculating correlation values between each of the spreading codesgenerated by said addition spreading code generation means and areceived signal and selecting a group having a maximum correlation valueamong the calculated correlation values, and control means for judgingwhether a number of spreading codes included in the group selected bysaid group selection means is one or not, and inputting all of thespreading codes included in the selected group into said additionspreading code generation means when the number of the spreading codesis two or more, and further setting the spreading codes included in theselected group to be used at despreading processing to the receivedsignal when the number of the spreading code is one.
 6. A method foridentifying a spreading code, said method comprising: an additionspreading code generation step for dividing a spreading code group intoat least two groups and adding spreading codes included in each group toeach other at every chip to generate new spreading codes; a groupselection step for calculating correlation values between each of thespreading codes generated by said addition spreading code generationmeans and a received signal and selecting a group having a maximumcorrelation value among the calculated correlation values, and a controlstep for judging whether a number of spreading codes included in thegroup selected at said group selection step is one or not, and returningall of the spreading codes included in the selected group into saidaddition spreading code generation step when the number of the spreadingcodes is two or more, and further setting the spreading codes includedin the selected group to be used at despreading processing to thereceived signal when the number of the spreading code is one.
 7. Themethod for identifying a spreading code according to claim 6, wherein insaid group selection step, a next maximum correlation value being acorrelation value largest next to the maximum correlation value iscalculated, and a difference between the next maximum correlation valueand the maximum correlation value is calculated, and further saidaddition spreading code generation step is controlled so that at leastone group of each of the groups after being grouped is divided at everyarbitrary number of the spreading codes to increase a number of thegroups when the difference is smaller than an arbitrary threshold value.8. The method for identifying a spreading code according to claim 6,wherein in said group selection step, said addition spreading codegeneration step is controlled so that combinations of the spreadingcodes included in each of the groups after being grouped are changedwhen the difference between the next maximum correlation value and themaximum correlation value is smaller than an arbitrary threshold value.9. The method for identifying a spreading code according to claim 6,wherein in said group selection step, a next maximum correlation valuebeing a correlation value largest next to the maximum correlation valueis calculated, and a difference between the next maximum correlationvalue and the maximum correlation value is calculated, and increase of anumber of the groups by dividing at least one group of each of thegroups after being grouped at every arbitrary number of the spreadingcodes is instructed when the difference is smaller than an arbitrarythreshold value, and/or change of combinations of the spreading codesincluded in each of the groups after being grouped or after beingdivided is instructed when the difference between the next maximumcorrelation value and the maximum correlation value is smaller than thearbitrary threshold value.